Polyimide resins are widely used as electronic materials such as protecting materials and insulating materials in liquid crystal display devices and semiconductors for high mechanical strength, heat resistance, insulating property and solvent resistance as their common characteristic properties. Recently, they are expected to also find utility as optical communication materials such as optical waveguide materials.
In recent years, the developments in these fields are remarkable, resulting in a demand for ever-increasing higher characteristics on materials to be used. Described specifically, such materials are expected to be equipped not only with excellent heat resistance and solvent resistance but also with many performances corresponding to their applications.
As a particularly important property, high transparency can be mentioned. As one of methods for realizing this transparency, it has already been reported to obtain a polyimide, which is relatively low in coloration and has high transparency, by obtaining a polyimide precursor through a polycondensation reaction between an alicyclic tetracarboxylic dianhydride and an aromatic diamine and then imidating the precursor (see Patent Documents 1 and 2).
The development of new polyimides having excellent properties is, however, desired under the situation in recent years that there is also an increasing demand for the use of polyimides of high heat resistance, solvent solubility and transparency in the field of electronic materials making use of light.
As a method for realizing this transparency, a wholly-alicyclic polyimide can be expected by obtaining a wholly-alicyclic polyimide precursor through a polycondensation reaction between an alicyclic tetracarboxylic dianhydride and an alicyclic diamine and then imidating the precursor.
However, a polyimide available from 1,2,3,4-cyclobutanetetracarboxylic-1,2:3,4-dianhydride (abbreviated as “CBDA”), a representative compound among conventional alicyclic tetracarboxylic dianhydrides, and an alicyclic diamine was so brittle that it was not usable as films. No film made of a wholly-alicyclic polyimide and having stable strength has been found yet accordingly.
There are certain examples in which bicyclo[2.2.0]hexane-2,3,5,6-tetracarboxylic-2,3:5,6-dianhydride (abbreviated as “BHA”), one of monomers for polyamic acids and polyimides of the invention, was synthesized by the following process.

As shown by Scheme 1, 3-cyclobutene-1,2-dicarboxylic anhydride (abbreviated as “CBA”) is synthesized by a photoreaction between acetylene (abbreviated as “AC”) and maleic anhydride (abbreviated as “MA”). Subsequently, as shown by Scheme 2, BHA is synthesized by a photoreaction between CBA and MA (see Non-patent Document 1).
It is to be noted that as shown by Scheme 3, CBA can also be synthesized by the process that obtains 3,4-dichlorocyclobutane-1,2-dicarboxylic anhydride (abbreviated as “DCBA”) through a photoreaction between 1,2-dichloroethylene (abbreviated as “DCE”) and MA and then reacts DCBA with zinc and acetic anhydride (see Non-patent Document 2).
There was, however, no example in which a polyamic acid or polyimide was synthesized using BHA.
Patent Document 1: JP-B 2-24294
Patent Document 2: JP-A 58-208322
Non-patent Document 1: Chemische Berichte, 123, 1869-1879 (1990)
Non-patent Document 2: Synthesis, 4, 574-576 (1999)